PCR diagnosis of Candidosis and Aspergillus

Barton, R. C, Hopwood, V and Evans, E. G. V.

Abstract:

Fungal infections are becoming increasingly important with the increase in immunocompromised hosts. The corresponding need to develop improved methods of diagnosis stems from the limits in sensitivity and specificity of antibody and antigen detection methods. We have tested techniques for the detection of fungal DNA in clinical samples using the polymerase chain reaction (PCR) and primers specific for universal and Candida fungal rDNA sequences, Candida albicans repeated sequences and Aspergillus fumigatus proteinase gene sequences. The sensitivity of detection of C.albicans in cells in vitro depends upon the primer used. The sensitivity correlated inversely with the size of product amplified. Primers amplifying larger products were less sensitive than those amplifying smaller ones. Using a primer pair recognising C.albicans 5S rDNA which amplifies a 103bp product as few as 5 c.f.u of C.albicans could be detected in a volume of 200ul. There were no differences in in vitro detection sensitivity between three different strains of C.albicans. These results suggest that PCR does have the potential to become a highly specific and sensitive diagnostic tool for invasive fungal disease.